A detailed RFLP map of cotton, Gossypium hirsutum x Gossypium barbadense: chromosome organization and evolution in a disomic polyploid genome.

TLDR

The study employed a detailed RFLP map to investigate chromosome organization and evolution in the disomic polyploid cotton Gossypium hirsutum × Gossypium barbadense. The authors constructed a map of 705 RFLP loci across 41 linkage groups totaling 4675 cM, using the cotton genome’s ~400‑kb per cM density to enable map‑based gene cloning. The map showed that 46.2 % of nuclear DNA probes distinguish the two species, that the A and D subgenomes have similar recombinational lengths but differ in repetitive DNA content, and identified 11 pairs of homoeologous chromosomal regions—most involving inter‑subgenome chromosomes—suggesting a recent 1.1–1.9 Myr polyploidization event and an earlier ~25 Myr event, thereby providing a framework for studying chromosome evolution and exploiting cotton genetic resources.

Abstract

Abstract We employ a detailed restriction fragment length polymorphism (RFLP) map to investigate chromosome organization and evolution in cotton, a disomic polyploid. About 46.2% of nuclear DNA probes detect RFLPs distinguishing Gossypium hirsutum and Gossypium barbadense; and 705 RFLP loci are assembled into 41 linkage groups and 4675 cM. The subgenomic origin (A vs. D) of most, and chromosomal identity of 14 (of 26), linkage groups is shown. The A and D subgenomes show similar recombinational length, suggesting that repetitive DNA in the physically larger A subgenome is recombinationally inert. RFLPs are somewhat more abundant in the D subgenome. Linkage among duplicated RFLPs reveals 11 pairs of homoelogous chromosomal regions-two appear homosequential, most differ by inversions, and at least one differs by a translocation. Most homoeologies involve chromosomes from different subgenomes, putatively reflecting the n = 13 to n = 26 polyploidization event of 1.1-1.9 million years ago. Several observations suggest that another, earlier, polyploidization event spawned n = 13 cottons, at least 25 million years ago. The cotton genome contains about 400-kb DNA per cM, hence map-based gene cloning is feasible. The cotton map affords new opportunities to study chromosome evolution, and to exploit Gossypium genetic resources for improvement of the world's leading natural fiber.